Problem: If $a + b = -1$ and $x + y + z = 8$, what is $-7b + 10z + 10y - 7a + 10x$ ?
Solution: $= -7a - 7b + 10x + 10y + 10z$ $= (-7) \cdot (a + b) + (10) \cdot (x + y + z)$ $= (-7) \cdot (-1) + (10) \cdot (8)$ $= 7 + 80$ $= 87$